1. Field of the Invention
The present invention relates to methods and apparatus for automatically wrapping each of a series of articles in plastic, especially open trays filled with food products to be secured and protected in the tray.
2. The Prior Art
Automatic wrapping machines have found wide use in providing a thin, clear, and tough plastic film to a variety of articles, large and small. A major use of such machines is found in retail food stores, wherein plastic or fiber trays are filled with meat or vegetable products and sealed on all sides by a thin plastic wrap. The wrap contains the contents and protects them against contamination and also facilitates handling and sale of the product. Such wrapping of produce is done at the retail site, and machines are frequently operated by relatively inexperienced personnel, thus requiring that the machines be simple to use and safe, as well as efficient and quick in operation.
Generally, prior art devices have employed at least one elevator in the folding, wrapping, and sealing processes. In these machines, the package or tray starts at one level and is at some point lifted to a higher level for folding or stretching the film over the article. U.S. Pat. No. 3,378,990, issued to the present inventor, is representative of modern, compact semi-automatic wrapping machines. U.S. Pat. No. 3,791,101 discloses placing the film curtain across the path of advance of a package, whereby motion of the package from one support surface to the next wraps the front, bottom, and top of the package in the plastic film for subsequent formation of a lap seam on the rear of the package.